Generally, through-air-drying papermaking processes include several steps. An aqueous dispersion of papermaking fibers is formed into an embryonic web on a foraminous member, such as Fourdrinier wire. This embryonic web is associated with a deflection member having a macroscopically-planar, and preferably non-randomly patterned network surface which defines within the deflection member a plurality of fluid-permeable deflection conduits. In a continuous papermaking process, this deflection member is in the form of an endless papermaking belt. If the patterned network surface of the deflection member is substantially continuous, the plurality of deflection conduits comprises discrete conduits isolated from one another. If the patterned network surface of the deflection member comprises a plurality of isolated from one another protuberances, the plurality of conduits form a substantially continuous area. The papermaking fibers are deflected into the deflection conduits, and water is removed through the deflection conduits, thereby an intermediate web is formed. The intermediate web is then dried and, if desired, is foreshortened by creping.
The papermaking belt comprising the deflection member is described in several commonly-assigned U.S. Patents: U.S. Pat. No. 4,514,345, issued Apr. 30, 1985 to Johnson et al.; U.S. Pat. No. 4,528,239, issued Jul. 9, 1985 to Trokhan; U.S. Pat. No. 5,098,522, issued Mar. 24, 1992; U.S. Pat. No. 5,260,171, issued Nov. 9, 1993 to Smurkoski et al.; U.S. Pat. No. 5,275,700, issued Jan. 4, 1994 to Trokhan; U.S. Pat. No. 5,328,565, issued Jul. 12, 1994 to Rasch et al.; U.S. Pat. No. 5,334,289, issued Aug. 2, 1994 to Trokhan et al.; U.S. Pat. No. 5,431,786, issued Jul. 11, 1995 to Rasch et al.; U.S. Pat. No. 5,496,624, issued Mar. 5, 1996 to Stelljes, Jr. et al.; U.S. Pat. No. 5,500,277, issued Mar. 19, 1996 to Trokhan et al.; U.S. Pat. No. 5,514,523, issued May 7, 1996 to Trokhan et al.; U.S. Pat. No. 5,554,467, issued Sep. 10, 1996, to Trokhan et al.; U.S. Pat. No. 5,566,724, issued Oct. 22, 1996 to Trokhan et al.; U.S. Pat. No. 5,624,790, issued Apr. 29, 1997 to Trokhan et al.; U.S. Pat. No. 5,628,876 issued May 13, 1997 to Ayers et al.; U.S. Pat. No. 5,679,222 issued Oct. 21, 1997 to Rasch et al.; and U.S. Pat. No. 5,714,041 issued Feb. 3, 1998 to Ayers et al., the disclosures of which patents are incorporated herein by reference.
Deflection of the papermaking fibers into the deflection conduits of the deflection member can be induced by, for example, application of differential fluid pressure to the embryonic web. One preferred method of applying the differential pressure comprises exposing the embryonic web to a vacuum through the deflection conduits of the deflection member. A sudden application of the differential fluid pressure to the fibers tends to separate some of the fibers deflected into the deflection conduits from the web and from one another. In addition, as a result of a sudden application of the pressure differential to the web, a certain number of partially dewatered fibers separated from the embryonic web could completely pass through the conduits of the deflection member. These phenomena cause formation of so-called "pinholes" in the finished paper web, and also may lead to clogging of the vacuum dewatering machinery with the fibers separated from the web.
This undesirable creation of the pinholes may be mitigated by providing a leakage between the deflection member and the papermaking equipment creating the fluid pressure differential. One way of creating such a leakage comprises providing surface texture irregularities in the backside network of the deflection member. Commonly-assigned U.S. Patents Nos.: U.S. Pat. No. 5,098,522 issued Mar. 24, 1992 to Smurkoski et al.; and U.S. Pat. No. 5,364,504 issued Nov. 15, 1994 to Smurkoski et al. disclosed a process of making a backside textured belt, comprising casting a photosensitive resinous material over and through a reinforcing structure while the reinforcing structure travels over a textured working surface. Commonly-assigned U.S. Pat. No. 5,275,700, issued Jan. 4, 1994 to Trokhan et al. disclosed a process of making a backside textured belt, comprising applying a coating of a photosensitive resin to the reinforcing structure and pressing the reinforcing structure into a deformable surface so that the deformable surface forms protrusions which exclude resin from certain areas, thereby creating a textured backside of the belt. Commonly-assigned U.S. Pat. No. 5,334,289 issued Aug. 2, 1994 to Trokhan et al. discloses a process for making a backside textured belt, comprising applying a coating of photosensitive resin to a reinforcing structure which has opaque portions, and then exposing the resin to curing radiation through the reinforcing structure. The foregoing patents are incorporated herein by reference.
Another way of mitigating the undesirable creation of the pinholes, developed by the present assignee, comprises making the belt having deflection conduits such that a substantial portion of each conduit is not less than about 45 mils in each of the conduit's dimensions (measured in the general plane of the belt, i. e., an X-Y plane), as disclosed in commonly-assigned U.S. Pat. No. 5,679,222 issued Oct. 21, 1997 to Rasch et al., which is incorporated herein by reference.
Still, the search for improved products has continued.
The present invention provides a novel process for making an improved papermaking belt comprising a reinforcing structure and a resinous framework joined thereto. It is a benefit of the present invention to provide a novel process for making a backside-textured papermaking belt. Another benefit of the present invention is that it provides a novel process for making a papermaking belt in which the depth of penetration of the resin into the reinforcing structure is controllable such that the resin penetrates a predetermined portion of the thickness of the reinforcing structure, so as to provide acceptable bonding of the resin to the reinforcing structure, while maintaining the flexibility of the reinforcing structure, as well as the permeability to air and water. Still another benefit of the present invention is that it provides a process for reducing the amount of the resinous material required for making the belt.